The present invention relates to low temperature curable coatings, more particularly to addition curable organopolysiloxane coatings that cure rapidly at low temperature.
Addition curable release coating compositions and their use as release coatings are known, see, for example, coassigned U.S. Pat. No. 4,448,815. Alayer of such coating is typically applied to a substrate, such as paper, from a reactive coating bath which contains an alkenyl-functional organopolysiloxane, a hydride-functional organopolysiloxane, an organoplatinum complex and a cure inhibitor. Once applied, the layer of coating is cured by exposing the coated substrate to elevated temperature.
The cure inhibitor retards cure of the coating and enables a balance between a long useful coating bath life at low temperature and rapid cure speed at elevated temperature to be maintained. There is a constant desire in the art to provide increased cure speed without compromising bath life.
The need to subject the coated substrate to elevated temperature to cure the coating layer introduces some drawbacks to the use of the process for addition cure organopolysiloxane release coatings. These drawbacks are in the form of energy costs, a need to rehydrate coated paper substrates after curing and a limited ability to use such coatings to coat temperature sensitive substrates, such as, for example, some polymer films. Due to these drawbacks, there is a desire in the art to provide coatings that are curable at lower temperature without compromising bath life.
The present invention provides a method of making a coated substrate comprising:
applying a coating composition to a substrate, wherein the coating composition comprises an alkenyl functional compound and a hydride functional compound, and the substrate comprises a catalytically effective amount of a platinum group metal catalyst having the formula ZxPt(0)Ly wherein L comprises an electron-withdrawing ester ligand, a quinone-based ligand, or combination thereof, y is in a range between about 1 and about 4, Z comprises a coordinating ligand, x is in a range between 0 and about 3, and x+y is in a range between about 2 and about 4; and
allowing the coating composition to cure.
The present invention further provides a system for making a coated substrate comprising a coating composition, said coating composition comprising an alkenyl functional compound and a hydride functional compound, and a substrate having a platinum group metal catalyst having the formula ZxPt(0)Ly wherein the catalyst is disposed on at least one surface of the substrate in an amount effective to catalyze cure of the coating composition when the coating composition is applied to the substrate.
The present invention further provides a catalyzed article comprising a substrate comprising papers, polymer films, polymer coated papers, metal foils, or combinations thereof, and a platinum group metal catalyst having the formula ZxPt(0)Ly disposed on at least one surface of the substrate.